Solar cell and method for manufacturing the same

Abstract

A method for manufacturing a solar cell is discussed. The method may include injecting first impurity ions at a first surface of a substrate by using a first ion implantation method to form a first impurity region, the substrate having a first conductivity type and the first impurity region having a second conductivity type, heating the substrate with the first impurity region to activate the first impurity region to form an emitter region, etching the emitter region from a surface of the emitter region to a predetermined depth to form an emitter part, and forming a first electrode on the emitter part to connect to the emitter part and a second electrode on a second surface of the substrate, which is opposite the first surface of the substrate to connect to the second surface of the substrate.

1 . A method for manufacturing a solar cell, the method comprising:
 injecting first impurity ions at a first surface of a substrate by using a first ion implantation method to form a first impurity region, the substrate having a first conductivity type and the first impurity ions having a second conductivity type opposite the first conductivity type, and the first impurity region having the second conductivity type;   heating the substrate with the first impurity region to activate the first impurity region to form an emitter region from the first impurity region;   etching the emitter region from a surface of the emitter region to a predetermined depth to form an emitter part from the emitter region; and   forming a first electrode on the emitter part to connect to the emitter part and a second electrode on a second surface of the substrate, which is opposite the first surface of the substrate to connect to the second surface of the substrate.   
     
     
         2 . The method of  claim 1 , wherein the heating of the substrate heats the first impurity portion at 800° C. to 1100° C. in a nitrogen atmosphere. 
     
     
         3 . The method of  claim 1 , wherein the etching of the emitter region removes a portion of the emitter region from the surface of the emitter region to a depth of 5 nm to 20 nm. 
     
     
         4 . The method of  claim 3 , wherein the emitter region is etched by an etchant composed of nitric acid HNO 3 , hydrofluoric acid HF and pure wafer. 
     
     
         5 . The method of  claim 1 , wherein the heating of the substrate heats the first impurity portion at 800° C. to 1100° C. in an oxygen atmosphere. 
     
     
         6 . The method of  claim 5 , wherein the etching of the emitter region removes a portion of the emitter region from the surface of the emitter region to a depth of 20 nm to 35 nm. 
     
     
         7 . The method of  claim 6 , wherein the emitter region is etched by an etchant composed of hydrofluoric acid HF and pure wafer. 
     
     
         8 . The method of  claim 1 , wherein the emitter part comprises a first emitter portion having a first impurity doped thickness and a second emitter portion having a second impurity doped thickness greater than the first impurity doped thickness, and
 wherein the etching of the emitter region comprises:   selectively forming an etch prevention layer on the emitter region to expose a portion of the emitter region and to cover a remaining portion of the emitter region; and   etching the exposed portion of the emitter region from the surface of the emitter region to the predetermined depth using the etch prevention layer as a mask; and   removing the etch prevention layer,   wherein the etched exposed portion of the emitter region is formed as the first emitter portion and the remaining portion of the emitter region is formed as the second emitter portion.   
     
     
         9 . The method of  claim 1 , wherein the first impurity region comprises a first impurity portion having a first impurity doped thickness and a second impurity portion having a second impurity doped thickness greater than the first impurity doped thickness, and
 wherein the injecting of the first impurity ions forms the first and second impurity portions by use of a mask positioned at the first surface of the substrate and use of the first ion implantation method.   
     
     
         10 . The method of  claim 9 , wherein the mask comprises a first portion having a first exposing area for forming the first impurity portion and a second portion having a second exposing area for forming the second impurity portion, the first and second exposing areas being areas exposing the substrate in a unit area thereof. 
     
     
         11 . The method of  claim 9 , further comprising forming the first impurity region not having the first and second impurity portions at an entire first surface of the substrate by injecting the first impurity ions of the second conductivity type at the entire first surface of the substrate without a mask, before forming the first and second impurity portions of the first impurity region,
 wherein the forming of the first and second impurity portions of the first impurity region forms the first and second impurity portions by use of the mask positioned at the first impurity region not having the first and second impurity portions and use of the first ion implantation method.   
     
     
         12 . The method of  claim 1 , further comprising;
 injecting second impurity ions at a second surface of the substrate by using a second ion implantation method to form a second impurity region of the first conductivity type, the second surface being opposite the first surface of the substrate;   heating the substrate with the second impurity region to activate the second impurity region to form an surface field region from the second impurity region; and   etching the surface field region from a surface of the surface field region to a predetermined depth to form a surface field part from the surface field region,   wherein the second electrode is connected to the second surface of the substrate through the surface field part.   
     
     
         13 . The method of  claim 12 , wherein the surface field part comprises a first surface field portion having a first impurity doped thickness and a second surface field portion having a second impurity doped thickness greater than the first impurity doped thickness,
 wherein the etching of the surface field region comprises:   selectively forming an etch prevention layer on the surface field region to expose a portion of the surface field region and to cover a remaining portion of the surface field region;   etching the exposed portion of the surface field region from the surface of the surface field region to the predetermined depth using the etch prevention layer as a mask; and   removing the etch prevention layer,   wherein the etched exposed portion of the surface field region is formed as the first surface field portion and the remaining portion is formed as the second surface field portion.   
     
     
         14 . The method of  claim 13 , wherein the second electrode is in contact with the second surface field portion and is connected to the second surface of the substrate through the second surface field portion. 
     
     
         15 . The method of  claim 14 , wherein the first and second surfaces of the substrate are light incident surfaces on which light is incident. 
     
     
         16 . The method of  claim 12 , wherein the second impurity region comprises a first impurity portion having a first impurity doped thickness and a second impurity portion having a second impurity doped thickness greater than the first impurity doped thickness,
 wherein the injecting of the second impurity ions forms the first and second impurity portions by use of a mask positioned at first surface of the substrate and use of the second ion implantation method.   
     
     
         17 . The method of  claim 16 , wherein the mask comprises a first portion having a first exposing area for forming the first impurity portion and a second portion having a second exposing area for forming the second impurity portion, the first and second exposing areas being areas exposing the substrate in a unit area thereof. 
     
     
         18 . The method of  claim 16 , further comprising forming the second impurity region not having the first and second impurity portions at an entire second surface of the substrate by injecting the second impurity ions of the first conductivity type at the entire second surface of the substrate without a mask, before forming the first and second impurity portions of the second impurity region,
 wherein the forming of the first and second impurity portions of the second impurity region forms the first and second impurity portions by use of the mask positioned at the second impurity part not having the first and second impurity portions and use of the second ion implantation method.   
     
     
         19 . The method of  claim 16 , wherein the second electrode is in contact with the second surface field portion and is connected to the second surface of the substrate through the second surface field portion. 
     
     
         20 . The method of  claim 19 , wherein the first and second surfaces of the substrate are light incident surfaces on which light is incident. 
     
     
         21 . A solar cell, comprising:
 a substrate into which an impurity of a first conductivity type is doped;   an emitter part positioned at a first surface of the substrate, into which an impurity of a second conductivity type opposite the first conductivity type is doped, and comprising a first emitter portion having a first impurity doped thickness and a second emitter portion having a second impurity doped thickness greater than the first impurity doped thickness;   a first electrode positioned at the second emitter portion and connected to the second emitter portion; and   a second electrode positioned at a second surface of the substrate and connected to the substrate, the second surface being opposite the first surface of the substrate,   wherein a junction surface between the first emitter portion and the substrate is positioned at a same height as a junction surface between the second emitter portion and the substrate, and a damage amount existing at the second emitter portion is more than a damage amount existing at the first emitter portion.   
     
     
         22 . The solar cell of  claim 21 , further comprising an anti-reflection layer positioned on the first emitter portion of the emitter part. 
     
     
         23 . The solar cell of  claim 22 , further comprising a surface field part positioned between the second surface of the substrate and the second electrode and doped with an impurity of the first conductivity type. 
     
     
         24 . The solar cell of  claim 22 , wherein the surface field part comprises a first surface field portion having a third impurity doped thickness and a second surface field portion having a fourth impurity doped thickness greater than the third impurity doped thickness,
 a first electrode positioned at the second emitter portion and connected to the second emitter portion, and   a damage amount existing at the second surface field portion is more than a damage amount existing at the first surface field portion.   
     
     
         25 . The solar cell of  claim 24 , wherein the second electrode is positioned on the second surface field portion and connected to the second surface field portion. 
     
     
         26 . The solar cell of  claim 25 , wherein the first and second surfaces of the substrate are light incident surfaces on which light is incident.